1. Field of the Invention
The present invention relates to a continuous shear deformation device, and more particularly, to a continuous shear deformation device suitable for making the amount of shear deformation of a material to be uniform throughout upper and lower parts of the material, increasing the amount of shear deformation, and occurring a rapid shear deformation.
2. Description of the Background Art
The shear deformation process is a process of obtaining a sheared material by passing a material into a mold for shear deformation having a molding path at which a curved portion is formed, and allowing shear deformation of the material to occur at the curved portion. This process has the object of fabricating a material of high strength and high plasticity by improving the strength of the material and forming a texture having a certain direction.
The above-mentioned shear deformation processes includes equal channel angular pressing (ECAP), equal channel angular drawing (ECAD), continuous ECAP process, and so on. FIGS. 1a, 1b, 2a, and 2b are views schematically illustrating shear deformation devices performing these shear deformation processes, respectively. As illustrated therein, the shear deformation devices are identical with one another in that each shear deformation device is constructed of molds 1, 2, 6, 7, 12, and 13 provided with molding paths 3, 8 and 14 having a curved portion shown in dotted line, but they are different from one another with respect to a means for applying power in order to passing materials 5 and 9 through the molds 3, 8 and 14.
Among these shear deformation processes, in case of equal channel angular pressing by which the material 5 is pushed out by a punch 4, only a sheared material of a limited length is obtained. Once the material is scalped, the next material can be provided only after extracting the punch 4 from the molds 1 and 2, so it is impossible to continuously mass-producing sheared materials. In case of equal channel angular drawing, although it is possible to mass-produce sheared materials, it is difficult to practically use this process because it has little effect for shear deformation. For the continuous mass production of materials having an appropriate amount of shear deformation, a continuous shear deformation device illustrated in FIGS. 2a and 2b which uses rotary guide apparatuses 10, 11, 15, and 16 in place of the punch 4 in order to continuously perform equal channel angular drawing is suitable.
However, the conventional continuous shear deformation device schematically illustrated in FIGS. 2a and 2b has the following problems.
First of all, in case of the continuous shear deformation device as illustrated in FIG. 2a, the friction surface between the material 9 and rotary rolls 10 and 11 of the rotary guide apparatus is so small that it is difficult to effectively push the material 9 into the molds 6 and 7. That is, the power for shear deformation of the material 9 in a curved portion, which is a part of the molding path 8 in the molds 6 and 7, and the power for overcome the friction force of the contact portion between the material 9 and the molds 6 and 7 must be applied to the material. Nevertheless, in case of the device illustrated in FIG. 2a, the friction surface between the material 9 and the rotary rolls 10 and 11 is so small that the above powers cannot be effectively transferred from the rotary guide apparatuses 10 and 11 toward the direction of the material.
In addition, as illustrated in FIG. 2b, in case of the continuous shear deformation device constructed in such a manner that the friction surface between the material 9 and the rotary roll 15 is increased, the above powers can be effectively transferred from the rotary guide apparatuses toward the direction of the material. However, it is difficult to machine a contact portion A simultaneously contacting the rotary guide apparatuses and the material, and the buckling phenomenon of the material is occurred due to the gap between the contact portion A and the material 9.
In addition, the conventional continuous shear deformation device illustrated in FIGS. 2a and 2b has a problem that the material is not tightly attached to a lower mold in the curved portion in the mold, thus making the amount of shear deformation of a lower part of the material insufficient. FIG. 3 is a view illustrating the calculation of the amount of shear deformation of a material in a curved portion in a mold by simulation. By this, it is known that a board plank is not completely attached to a molding surface at the curved portion directed by an arrow, but is isolated therefrom. Accordingly, it is known that the amount of shear deformation in the lower portions of the material is not sufficient as compared to other portions, which is confirmed by an actual experiment performed by the inventors. That is, the scales indicated in a vertical direction on the sides prior to shear deformation of the material as shown in FIG. 4a are indicated as shown in FIG. 4b after passing through the continuous shear deformation device, which indicates that the amount of shear deformation in the lower portions of the material is smaller than that in other portions.
In addition, in the conventional discontinuous or continuous shear deformation devices described above, a curved portion is formed at the center of molding path 3, 8 and 14 having the same width, and thus the movement of the material is inhibited by the friction at the molding path excepting the curved portion at which shear deformation is actually occurred. Therefore, a considerable power plus the power required for shear deformation in the curved portion has to be additionally applied to the materials, which is ineffective.
In addition, there is another problem that the life span of the molds is not long because the abrasion occurred adjacent the curved portion which receives the largest friction force from the molding paths rapidly performed as compared to other portions.
Accordingly, the objects of the present invention disclosed to overcome the problems encountered in the conventional art will now be described.
It is an object of the present invention to provide a continuous shear deformation device capable of effectively transferring power in the direction of a material from a rotary guide apparatus without difficulty in fabricating a mold, and thus smoothly performing shear deformation of the material.
It is another object of the present invention to provide a continuous shear deformation device having no possibility of buckling phenomenon of the material occurred at the entrance of a molding path.
It is still another object of the present invention to provide a continuous shear deformation device capable of obtaining an uniform and sufficient amount of shear deformation throughout the material by assuring contact between a lower part of the material and a curved portion in a molding path at which the material is sheared.
It is another object of the present invention to provide a continuous shear deformation device capable of assuring a longer life span of the mold.
It is another object of the present invention to provide a continuous shear deformation device which can be compatibly used in response to materials of different thickness, that is, from thin-walled materials to thick-walled materials.
To achieve the above objects, there is provided a continuous shear deformation device in accordance with the present invention which includes: a mold having a molding path which a material passes through; and a rotary guide apparatus for guiding the material to the molding path, wherein a curved portion is constructed by collaboration between the rotary guide apparatus and the opening of the molding path, so that shear deformation may be occurred at the position at which the material is inserted into the molding path from the rotary guide apparatus.
As the rotary guide apparatus, a rotary roll contacting materials, or a belt transmission for moving materials by rotating a belt contacting the materials can be used. As the belt, belts of various shapes, such as a roof having a plurality of polyhedron blocks sequentially connected to the same and a belt of which the inside is chain-shaped, can be used. In addition, the rotary guide apparatus can be a combination of the rotary roll and the belt transmission. For example, the rotary guide apparatus can be constructed by installing a plurality of rotary rolls at one side and a belt transmission at the other side. Also, in case of using the belt transmission, it is possible to use a combination of belts of various shapes.
To reinforce the friction between the material and the rotary guide apparatus, it is preferable that irregularity is formed on the surface contacting the material of the rotary guide apparatus, that is, the surface of the rotary roll or the belt. This is achieved by coating the surface using an additional material of high friction coefficient, or by increasing the surface roughness by forming irregularity by mechanical processing. In addition, it is also possible to fabricate a portion directly contacting the material throughout the entire rotary guide apparatus by using a material of high friction coefficient.
And, it is preferable that a lateral guide for guiding and supporting the lateral parts of the material is installed at the rotary guide apparatus in order to prevent the material from being bilaterally moved while passing through the mold for the purpose of shear deformation. Such a lateral guide can be installed at one of the rotary guide apparatus and the mold, or at both of them.
In addition, it is preferable to construct the continuous shear deformation device by installing the rotary guide apparatus and the mold as one part of a continuous processing equipment, in order to perform shear deformation as one process step in a continuous process for processing the material by means of multiple process steps. For example, the material can be heated at a desired temperature, and then can be sheared. In this case, it is possible to connect the continuous shear deformation device to an apparatus for heating the material. In a case where a cast or rolled material is directly sheared, the continuous shear deformation device can be connected to a continuous casting apparatus or a rolling apparatus. In addition, the continuous shear deformation device can be connected to an apparatus for cooling, cutting, flattening, or winding the material extracted from the continuous shear deformation device.
With respect to this, the thickness of the material before passing through the rotary guide apparatus may be larger than the thickness of the material after passing through the same. For example, it can be assumed that the rotary guide apparatus is constructed by using a series of pairs of rotary rolls, the spacing between which being gradually reduced. In this case, it is possible to provide a compatible continuous shear deformation device to materials of different thickness, for example, thin-walled materials of a thickness less than 0.5 mm and thick-walled materials, irrespective of thickness of the materials, by rolling the materials corresponding to the clearance spacing of a material supply path having a gradually reduced width formed by the rotary guide apparatus, without any additional processing of the materials.
It is natural that the amount of shear deformation of the material is adjusted according to the angle of the curved portion. Moreover, it is also possible to additionally form one or more curved portions at the molding path of the mold besides the curved portion at the opening, so that the material is sheared more than two times while passing through the molding path.
Friction is most apparent in the vicinity of the curved portion in the mold at which shear deformation is occurred. Thus, in order to improve the abrasion resistance of the vicinity of the curved portion, it is possible to fabricate that portion using an ultralight material. At this time, the vicinity of the curved portion can be coated with the ultralight material, or it can be entirely made of the ultralight material.
In addition, some part including the curve portion in the mold, which is greatly abraded during shear deformation, can be constructed as a separate, replaceable component.
In order to reduce the power applied in the direction of the material by decreasing the friction between the mold and the material, it is preferable that a lubricant applicator is additionally included.
As another construction for reducing friction force, it is preferable that the width of the molding path before the curved portion is formed to be larger than that of the molding path behind the curved portion, centering around the position spaced apart from the curved portion in the direction of the material, thereby reducing unnecessary friction between the material and the molding path.
Although the width of the molding path before the curved portion is identical with that of the molding path behind the curved portion in general, it is also possible to design and fabricate a mold of which the widths of the molding path before and behind the curved portion are different from each other, so that the thickness of the material before shear deformation is different from that of the material after shear deformation.